Updated September 25, 2026.
This is a protocol that I heard about many years ago for getting rid of Giardia. It is not “my” protocol and I can’t guarantee results. I didn’t develop it, but I’ve used it hundreds of times successfully (and safely) in cats and dogs.
Giardia lamblia is a protozoal parasite found around the world. It lives in water, particularly wild rivers, streams, and lakes.
This protocol uses digestive enzymes on an empty stomach. Although it has not been tested with other protozoal parasites, it could theoretically have activity against Tritrichomonas foetus or similar protozoa. One of my clients reported successfully using the protocol for a cat with Tritrichomonas, but that’s just one case.
The following protocol has never been tested in a controlled clinical trial, and I do not claim that it is an established treatment. However, laboratory research shows that proteolytic enzymes can interact directly with Giardia structures and its life cycle. Whether that has anything to do with the apparent effects of this particular protocol is unknown, but I think the question deserves study.
The Protocol
You’ll need a bottle of digestive enzymes (plant or fungal based) and one or more syringes; you can usually talk your vet into giving you a few 3 or 6 cc syringes (without needles).
Do not use products containing solely animal-based enzymes or pancreas extracts. While such products will not hurt your pet, plant or fungal enzymes are more likely to survive the stomach’s acidic environment, and still be working when they get to their destination. Also avoid products with extra ingredients, like whey protein, probiotics, or prebiotics. We want the purest enzyme product possible.
You can buy enzymes at any health food store, or order online. However, avoid enzymes in combination with herbs or food supplements.
The products I’ve used have contained protease, amylase, and lipase (some also contain cellulase). These digest protein, starch, and fat, respectively. The current best product I can find is NOW Plant Enzymes.
However, it is most likely the proteases that are most important If you have trouble finding a good combo product, you can theoretically use just proteases (such as bromelain or papain) alone.
INSTRUCTIONS:
Enzymes MUST be given on an empty stomach for best results.
Take 1 dose (according to label directions for pet products) or 1 capsule of enzymes (human product) for each animal to be treated. If you’re using a capsule, open it and just use the contents. Do not give the capsule whole.
Mix the powder or capsule contents with a tiny amount of water to make a slurry. Use the syringe to give the slurry by mouth. In most cases it’s easiest to insert the syringe in the corners of the mouth between or behind teeth and squirt. The mixture does not taste that bad, but some cats are just not gracious about taking meds. So, be careful, but firm.
Give enzymes three times a day. It is not necessary that they be evenly spaced. Before work, after work, and at bedtime is a schedule that works for many people. Give 1/2 to 1 hour before meals.
Round 1
Give one (1) dose of digestive enzymes 1/2 to 1 hour before morning and evening meals, and one (1) dose at bedtime. Take the syringe apart and rinse clean after each dose (otherwise the residue builds up and the plunger will stick). Repeat daily for eight (8) days.
Rest
Take a break for 7 days. This allows time for resistant cysts to “hatch.”
Round 2
Repeat digestive enzyme treatment for 7 days.
PRECAUTIONS
If you leave food out for your pet 24/7, this protocol will NOT work. Food must be given only in meals, separately from the enzymes (1/2 to 1 hour after the enzymes). (I recommend that cats be fed in discrete meals anyway. They are not cows and they don’t need to graze.)
Do not try to hide the enzymes in a pill pocket or a piece of cheese – remember, the tummy must be empty!
You may also add enzymes to your pet’s food to improve digestion overall, but mixing enzymes with food may dilute its effects.
The protocol must be done exactly as written for best results.
You are free to make any additions, substitutions, or changes you want to the protocol, but if you do, then it is no longer the same protocol and it may not work.